Disc drives are viewed by many as delicate and sensitive data storage devices. External vibrations and shocks can damage a disc drive and destroy large amounts of data. A typical disc drive has one or more circular metal discs, coated on both sides with a thin layer of magnetizable material. These discs can be mounted on a spindle that rotates them at a constant, high speed. For each surface (the top and the bottom of each disc), the drive has a read/write head. These heads are mounted on a head assembly that moves them in toward the spindle or out toward the edge of the disc.
Traditional disc drives are designed to keep the heads flying several microns above the surface of the discs. The air flow created between the heads and surface keeps the heads from touching the surface. If the head hits the surface too hard, the head will damage the surface (and possibly the head). In particular, if the head hits the surface and scraps off a portion of the magnetizable coating, data stored on that portion of the disc may be lost. External vibrations and shock can damage the disc drive by causing the head to hit the disc.
External vibrations and shock may be caused by packaging, transporting, assembling, and handling the disc drive. To reduce these damaging effects, the disc drives have been designed to meet specific, customer defined vibration and shock specifications. Specifically, many disc drives use shock absorbers to reduce the damaging effects of the customer defined specification loads.
Conventional shock absorbers may use shock mounts 110 to attach a bracket 112 to the disc drive 100 and isolate the disc drive 100 from vibration and shock, as represented by FIG. 1. The Z axis 102 is defined as the direction perpendicular to the top cover surface 104 of the disc drive 100. The X axis 108 is defined in the direction of the shortest edge and the Y axis 106 is defined in the direction perpendicular to the X axis. This shock mount design tends to protect the disc drive 100 from the customer specified shock. The design also protects the individual components inside the disc drive, such as the spindle/motor, head gimbal assembly, e-block arm to disc spacing, etc. However, the shock mount design is often times limited to only absorbing the customer defined shock load specification.
The shock mount design can be tested by using a shock mount test. In the shock mount test, engineers select a mounting orientation for the disc drive 100. The mounting orientation is related to a customer specified shock direction. The disc drive 100 is mounted on a table in accordance with the selected orientation. The table is then dropped onto a stopper. The stopper imparts a predefined amount of deceleration to the table and hence, to the disc drive 100. Shock mount designs that pass the shock mount test generally protect and isolate the disc drive 100 from the customer defined vibration and shock load specification.
As an alternative to the shock mount design, conventional disc drive systems may also use a shock absorbent jacket to protect the disc drive from vibration and shock. The shock absorbent jacket is made of a shock absorbing material that encloses the disc drive. However, like the shock mount design, the shock absorbent jacket generally protects and isolates the disc drive from the customer defined vibration and shock load specifications.
The shock absorbent jacket is tested using a three axes test. The three axes test comprises providing a perpendicular shock input on all six surfaces of the disc drive. The Z axis is defined as the direction perpendicular to the top cover surface of the disc drive. The top cover surface is the surface with the largest surface area. The X axis is defined in the direction of the longest edge of the disc drive and the Y axis is defined in the direction perpendicular to the X axis. The shock input provided by the three axes test is predictable and controlled. In particular, the disc drive is dropped from a specified height and direction which are proportional to the magnitude and direction of a customer defined shock specification.
The conventional shock absorbers, such as the shock mount design and the shock absorbent jacket, are typically not defined to absorb unpredictable vibrations and shocks. These shock absorbers frequently fail to protect the disc drive system from vibration and shocks produced in harsh environments. Instead, such shock absorbers may only protect the disc drive from the customer defined shock.
Thus, there is a need in the art for a shock absorbing apparatus that is capable of absorbing shocks in harsh and unpredictable environments.